Sforno on Exodus 3:15/ספורנו על שמות ג׳:ט״ו

1ויאמר עוד אלוקים אל משה כה תאמר אל בני ישראל, the Beney Yisrael that G’d refers to here are the elders of the people. (according to Rashi the people at large would not understand such thoughts.)

2ה' אלוקיכם, this is also the G’d of your patriarchs in addition to being the G’d possessing these virtues just mentioned. He had concluded a covenant with your patriarchs including all their offspring, so that this is part of My definition (name) זה שמי לעולם, forever as well as the name He already was known by previously before this additional attribute through the covenant with the patriarchs.

3זכרי לדור ודור, this is what wise men have figured out for themselves already since time immemorial that there must be a prime Cause, an eternal Being, not subject to change, i.e, to aging, weakening.